Method of making alkali hydroxids.



stra n s earns rice.

PHILIP B. SADTLER AND SAMUEL P. SADTLER, OF PHILADELPHIA, PENNSYLVANIA.

METHOD OF MAKING ALKALI HYDROXIDS.

No. err-eve.

Specification of Letters Patent.

Application filed September 25. 1907i Serial No. 394.503.

To all whom it may concern:

Be it known that we, PHILIP B. SADTLER and SAMUEL P. SADTLER, citizens of the United States, residing in the city of Philadelphia, county of Philadelphia, and State of Pennsylvania, have jointly invcnted'an Improved Method of Making Alkali Hydroxide, of which the following is a specification.

Cur invention relates to an improved method whereby an alkali sulfate such as,

when the roasted product comes to be dis-' solved, has, in the form of calcium hydroxid, a causticieing effect on the sodium carbonate first produced, with the result of a large production of sodium hydroxid or caustic soda.

It has been sought frequently to effect the decomposition of sodium sulfate by'heating it with. alumina (generally in the form of bauxite). Standard authorities (DammeWs Handbuch der Chem. l ealmologic, 1., .363) however sa with regard to this that a umina (bauxite) eeomposes the sulfate only in the ressure of steam at high temperatures. ihey state in addition that the decomposition maybe effected in the presence of carbon, but that, because of the formation of sodium sulfid, the oxid of iron present as an impurity reacts to form a soluble sulfid of iron and sodium, an undesirable contamination. A modification of this last method i nites a mixture of bauxite with alkali or a kalineearth sulfate andjust enough carbon to con-- vert the whole of the sulfate into sulfur dioxid without the formation of sul'lid, which would bring about impurity in the elurninateliquor, I

but this exact point has been found hard to determine in practice. It has also been'proposed to fuse bauxite with alkali sulfate and about one fifth its Weight of alkali sulfid, without carbon, and this was supposed to furnish a reaction which would liberate all the sulfur as sulfur dioxid. mixture of bauxite, alkali sulfate and pyrites, figuring tirely dehydrated at a low red heat.

the iron as ferric oxid, has also been sug gested. Another method r0 osed Was the Patented Jan. 21, 1908. i

the liberation of sulfur as sulfur dioxid and heating of alumina, an akai sulfate and metalhc'iron, Without access of air; the pro ducts claimed to be obtained being sodiuih I aluminate, ferrous sulfid, and ferric oxid,

Vi e have found that by the adoption of certain precautions it is possible tocompletely decompose the alkali. sulfate by heatstcam, of carbon, of sulfide, of iron, or any other ingredient. complete decomposition of the alkali sulfate and have founded upon this method for the production of caustic potash from the corresponding sulfate, which is made up of the following several steps. 1st. Alumina and alkali sulfate are so mixed and heated as to produce directly an alkali aluminate, with evolution of sulfur trioxid, sulfur dioxid and presumably oxygen. dissolved and a partial separation of the aluminium hydroxid is effected by agitation of the solution. 3rd. The further and complete decomposition of the alkali aluminate is effected by causticization with lime which I leaves the alkali hydroxid alone in solution.

In carrying out our process practically, with-for example sodium sulfate, we proceed as follows :The alumina (or bauxite) is ground very fine and mixed with sodium sulfate, using preferably an excess of alumina over the amount indicated by the molecular proportions. A mixtureof seven parts by Weight of the hydratedalumina or bauxite and live arts by weight of the anhydrous sodium su fate was found to ive excellent results, although we do not Wis -to be limited to this ratio, giving it merely as an example. Toueffect intimate admixture of the ingredients we have found it best after weighin outand mixing the ingredients to add so ncient Water to ust barely dissolve the-sodium sulfate. This asty mixture of alumina and saturated sol iition of sodium sulfate is carried down to dryness and leln .16 mass is preferably e ain g round very fine be fore being used for the roast, as it is necessary for a satisfactory yield that the mixed materials be in very intimate contact. The roasting that follows requires that the term perature be brought to about an incipient yellow heat or higher and not lower than 2nd. The aluminate is mg with alumina alone, Without the use of We have carried out this orange, when, if the materials are in intimate contact, the reaction proceeds very of equal molecu es.

rapidly, the product being a sintered mass.

This roasting takes place best withfree access.- of air and indeed, with a view. to thecollection and utilization pf thegaseousoxids of sulfur andvthe hastenin of the reaction, it

. I will probably be desira' 1e to have a slight suction applied, although the amount of air drawn through must not be enough to lower the tem erature of the furnace. Using the ratio 0 ingredients mentioned above we obtained a 98% yield. Upon leaching out the aluminate of soda formed and filtering from the excess of alumina used, we obtain asolution in which the alumina and sodium oxid-are ap roximately-in the ratio Utilizing the well known property of such a solution, we decom pose the,same by continued agitation with separation of the greater part'of the alumina in the form of aluminium hydroxid. We then filter from this the sodium aluminate remaining, of the approximate ratio of one alumina to six sodiumoxid in combination,

' and to this add milk of lime for the purpose of precipitating the remaining alumina in E Iaving described our invention, Y we clann:-- I 1 In the roduction of alkali hydroxid,

the method. w ich consists in intimately mixing an alkali sulfate with not less than about I smart an equal amount of alumina and heating the mixture to not lower than an orange heat,

2. In the production of alkali hydroxid, the method which consists in intimately mixing finely divided alkali sulfate and alumina in suchproportions and heating the mixture, in the absence of reducing agents, to such tem erature as to produce directly thereby an a kali alumina te.

3. In the method ofmakin alkali hydroxids, the method described 0 producing alkali aluminate, which consists in heating to at least an incipient yellow heat a mixture consisting of finely divided alkali sulfate and a larger amount of finely divided alumina.

- 4. The method of making alkali hydroxid which consists in intimately mixing finely divided alkali sulfate with at least an equal amount of alumina, heating the same to at least an incipient yellow heat untilan alkali aluminate is formed therefrom, decomposing the alkali. aluminate, and producing alkali hydroxid therefrom.

5. The method of making alkali hydroxid which consists in intimately mixing finely divided alkali sulfate with at least an equal amount of alumina, heating the same to at least an incipient yellow heat until an alkali ahnninate-is formed therefrom, decomposing the alkali aluminate by agitation to separate a portion of the combined alumina,

, and precipitating the remainder by the addition of milk of lime In testimony whereof we have hereunto set our names this 24th day of Se tember, Y

1907, in the presence of the subscri ing witnesses.

PHILIP B. sAnTLER. SAML. P. SADTLER. Witnesses: JAs. G; DENNY, Jr., ROBERT JAMES EARLEY. 

